CVE-2026-7273
Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
Zyxel GS1900 Series Switches
A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 21 September 2026. US federal agencies were required to remediate it by 24 September 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 2.5%, which is higher than 84.2% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-7273 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-7273.
What does CVE-2026-7273 affect?
CVE-2026-7273 affects Zyxel GS1900 Series Switches. A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
How severe is CVE-2026-7273?
CVE-2026-7273 is rated HIGH with a CVSS base score of 8.8. EPSS puts the probability of exploitation in the next 30 days at 2.5%, higher than 84.2% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 24 September 2026.
How should organisations respond to CVE-2026-7273?
Apply the vendor patch for Zyxel GS1900 Series Switches as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.